28 THE RELATION OF PLANTS TO TIDE-LEVELS 
The large, simple, tubular fronds of Hnteromorpha intestinalis are likewise 
characteristic of higher levels, especially in the neighborhood of fresh-water 
streams. Along these streams, however, when they are large enough to reach 
to the low-tide mark as single streams, we sometimes find the Hnteromorpha 
accompanying them downward to within the limits of our zone. For example, 
at 20 south by 590 east, beside the main stream at the head of the harbor, at 
the 1.5-foot level, H. intestinalis is usually quite abundant and of good size, 
though neither as abundant nor as large as it is, at somewhat higher levels, a 
few feet south of this. A very interesting patch of this Hnteromorpha is that 
growing on the bottom near 1,440 north, on the east shore. At this point the 
overflow pipe from an artesian well penetrates the wall of the wharf at the 4-foot 
level. At low tide the water from this pipe falls to the bottom, which is at 
about the 1.5-foot level, where the water splashes down upon pebbles and 
stones, and then runs off over the bottom toward low-water level. A circle of 
the bottom 4 feet in diameter, round about the point where this stream strikes, 
is covered by hundreds of plants of Hnteromorpha intestinalis, from 5 to 20 
mm. in diameter and 2 or 3 dm. in length. A few dozen plants are found 
scattered along the stream running from this circle down over the bottom, but 
this latter area is dominated by Ascophyllum. Near another fresh-water outlet 
100 feet north of this we have a similar sparse sprinkling of this Hnteromorpha 
which does not dominate any appreciable area. The factors affecting the distri- 
bution of Enteromorpha intestinalis will be mentioned in discussing its distribu- 
tion at higher levels, where it is more abundant. 
Ulothriz flacca was found but sparingly below the 1.5-foot level in April 
1911, though it was everywhere abundant just above this. 
PHAOPHYCEA. 
Ascophyllum and Fucus: What has just been said of the relative abundance 
of Enteromorpha in this belt is true also of Ascophyllum and its relative Fucus, 
two genera which, because of their similarity of distribution, may be discussed 
together. ‘These alge attain their greatest abundance in the next higher belt 
of vegetation, in the harbor, from 1.5 to 6 feet. (See plate 1x.) The rela- 
tively few plants found below the 1.5-foot level grow on stones, chiefly along the 
channel to the Outer Harbor or along that from the Creek. Occasionally plants 
or clumps may be found on stones or sunken logs along the shores of the harbor. 
Near the middle of the harbor these alge are rarely found, and then they are 
attached to small pebbles or shells which they have evidently dragged with them 
from higher levels in the Inlet. 
From the distribution of Fucus and Ascophylium found in the Outer 
Harbor, it is evident that these plants may grow abundantly at, and somewhat 
below, low-water mark. It is therefore probable that the sparseness of these 
algee below the 1.5-foot level in the Inner Harbor is due in part to the absence 
below the bases of the wharves of any proper substratum for their attachment. 
The abundance of shifting Ulva is another important factor, for these sheets 
would be sure to bury the relatively slow-growing rockweeds before they could 
attain any considerable size. 
Ectocarpus siliculosus var. amphibius: This form has been found below 
the 1.5-foot level in only one locality, near a deep portion of the channel of the 
